A series of bidentate ligands containing different heteroatoms and corresponding trivalent vanadium complexes are successfully synthesized,and their catalytic properties are evaluated in olefin polymerization to disclose the relationship between the catalytic performance and bidentate ligands in complex structure.It is found that under the activation of co-catalyst,all these vanadium complexes can efficiently catalyze ethylene polymerization to prepare linear polyethylene,showing an activity as high as 7 740 kg·(mol·h)-1.Combined with the addition of bulky ligand in the complex,vanadium complex C3 containing S＾N ligand exhibits the best thermal stability.C3 remains moderate activity at 80℃in ethylene polymerization,showing a catalytic activity of 5 560 kg·(mol·h)-1.In the copolymerization reaction between ethylene and polar monomers,these trivalent vanadium catalysts also show moderate activity and help to obtain the corresponding copolymers successfully.
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